MLK-23574-32 DTS: imx8mn: Update DDR4 EVK DTS and binding files

MLK-23574-32 DTS: imx8mn: Update DDR4 EVK DTS and binding files

Sync the DTS and binding files with v5.10.y kernel.
Some updates in u-boot:
1. Add alias for flexspi, usbotg1 and usbotg2.
2. Add usbotg2 nodes
3. Add i2c force idle pins
4. Update usbotg nodes to use excon
5. Add pmic and i2c to -u-boot.dtsi for SPL DM

Signed-off-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit 32cdd89a0e06bf40f8240cb7063c142321a16200)